The invention relates to a gate-valve, in particular a sanitary gate-valve which is used in the agricultural and food, pharmaceutical, cosmetic or other industries, where it is important to clean the gate-valve periodically.
The invention more particularly relates to a class of gate-valves, with single, double or other staunchness, for sanitary use for installations involving high liquid flow rates, for example in industries manufacturing food products.
It is known to use, for such applications, a gate-valve comprising a gate-valve body inside of which a gate-valve seat is formed having a stop surface delimiting the orifice of a pipe, a valve moving in a linear direction in the gate-valve body, the valve having an upper shoulder and a lower shoulder axially distanced from the upper shoulder, and a seal fitted between the two shoulders intended to stop the orifice of the pipe, the pipe having an internal peripheral surface which is parallel with the direction of displacement of the valve.
It is common to fit such gate-valves with a relatively soft seal, for example an elastomer seal, fitted around an inclined or curved portion of the end of the valve after having being expanded by heating. However this type of seal has poor resistance to chemical attack and consequently is not suitable for sanitary installations.
Recently recourse has been made to another type of seal, formed from a rigid material based on fluorinated resins of the PTFE type, which does not exhibit the disadvantage mentioned above.
Furthermore, as mentioned previously, it is important, in sanitary installations, to clean the gate-valve periodically in order to eliminate deposits of products which lodge more particularly between the seal and the valve. In fact these deposits of products generate bacteria which contaminate the food or other products. Consequently, it is essential that the seal can be easily withdrawn from the valve in order to be cleaned correctly. However, it is preferable to be able to clean the gate-valve with all of the components (valve, seal) in position as the dismantling of the gate-valve is a waste of time.